A display device is a device for visually displaying data information such as text, figures, and the like. The display devices include mobile phones, notebooks, televisions, and the like. A display device such as a television is provided to be connected to a set-top box or the like to receive a digital signal.
The display device may be provided with an input port capable of receiving a digital signal, and an external device, such as a set-top box or the like, outputting a digital signal may be provided with an output port. When the output port and the input port are connected, a digital signal is transmitted from the external device to the display device and video or audio information may be output to the display device according to the input digital signal.
Conventionally, a video or audio signal transmitted to the display device is formed in an analog type. A video signal and an audio signal are separately output as signals in an analog type. Therefore, a port for receiving a video signal and a port for receiving an audio signal are separately provided on the display device. Recently, a video or audio signal transmitted to a display device tends to be transmitted as a digital signal. However, since external devices transmitting signals in an analog type are still currently used, it is necessary for a recently produced display device to be provided with a method of receiving an analog signal.